The company said most of the work of the Belfast operation, located at Queen’s Road in the east of the city, will transfer to Glasgow.

A company statement insisted it would “endeavour” to offer the Belfast workers alternative employment.

However, Davy Thompson, regional co-ordinating officer for Unite - which represents 60 employees, added: “If they are talking about closing down, the only alternative employment will be in Glasgow.

“So it really depends whether people are prepared to up and move to Scotland to keep their jobs.”

Howden is American-owned, operating in more than 17 countries.

It is understood staff at the factory were only told of the threat to their jobs on Thursday.

A statement from the firm, which makes equipment for power generation and mining, said: “The company will fully consult on the proposals with employee representatives and trades union representatives immediately, and with individuals potentially affected thereafter.

“The purpose will be to look at opportunities to minimise the impact of these changes to our associates and the company will endeavour to offer suitable alternative employment to those affected if possible.”

Mr Thompson described the planned closure as a “savage blow to the workforce”.

“We are committed to securing the very best possible terms for all our members affected by this decision and keen to pursue any opportunities for redeployment provided by the company,” he said.

“This decision will end the company’s 134 year association with Belfast.

“With the announcement of the closure of the JTI factory in Ballymena, formerly Gallaher’s cigarettes, this means two of Northern Ireland’s oldest manufacturers have announced their closure in the period of six months, with the loss of almost 300 years of manufacturing experience.

“Northern Ireland has lost almost 2,000 manufacturing jobs in the last year.”

Mr Thompson said the owners of the company appear to have made the decision to close the plant “exclusively on the basis of lowering operating costs”.

He added: “It is highly concerning that despite Northern Ireland having the lowest wages in the UK, we are still losing in the global race-to-the-bottom.”